Wide-area networking systems serviced by ATM (Asynchronous Transfer Mode) have multiple nodes that are interconnected by high-speed data links. Each network has a plurality of nodes, which may each contain switching devices that regulate data traffic to user equipment. User equipment may be connected to the nodes.
Each node has a controller device and switch, which facilitate the calls through the node. The controller has processing, memory, and other resources to interpret, forward, and process messages and initiate other messages as appropriate, while the switch ordinarily handles the physical routing of messages among nodes and user terminals.
In a redundant high-availability private network-to-network interface (“PNNI”) routing protocol implementation, a redundant pair of controllers is used in the case of controller failure. Thus, each node has two controllers, one primary and one secondary. In order to ensure proper functioning, it is desirable to perform maintenance and testing on the links.